1. Field of the Invention
The present invention concerns a device for cleaning wiper elements for an inkjet print head of an ink dispenser. The invention is suitable for an inkjet printing device that is used for mail processing, addressing and franking machines, and other inkjet printing apparatuses.
2. Description of the Prior Art
The use of a sponge element in a franking machine of the Jetmail® type is described in European patent application EP 885 726 A1. This sponge element is attached to the print head and serves to wipe off the wiper lips that are arranged on the carriage of a cleaning and sealing station (RDS). The solution is expensive because more ink that must be wiped off and absorbed by the sponge also collects on the much larger (in comparison to HP print heads) print head surface of the special print head of the Jetmail®. Since, due to the large amount of ink, the absorption capacity of the sponge is soon exceeded, time-consuming and costly measures for suctioning the excess ink from the sponge element are required for maintenance.
For example, modern franking machines with inkjet technology use print heads from Hewlett Packard that have wiper elements in order to remove the excess ink from the print head. Either the print head travels over a stationary wiper element or the wiper element travels over the stationary head. The excess ink taken up by the wiper elements is stripped off by stripping elements (scrapers, (blades)). Since the HP print heads have a relatively small print head surface, this conventional arrangement is sufficient.
A device to clean an inkjet print head for a franking machine of the Centormail® type is known from European patent application EP 1 782 954 A1. The inkjet print head is a component of each ink cartridge. Two ink cartridges are arranged in a receptacle such that they can be exchanged. The receptacle is pivotable into a printing position so that the inkjet print head is stationary in a printing window of a guide plate for the flat mail pieces (printing media) during the printing. A cleaning and sealing station serves as a maintenance station and is likewise arranged such that it can be displaced below the guide plate and can be moved toward and away from the inkjet print head. A stripper is arranged separate from the print head mounted on a stripper mount, the latter being attached to the chassis. Two strippers serve to wipe off the wiper lips that are arranged on the carriage of a cleaning and sealing station (RDS) when the carriage is moved away from the inkjet print head again and travels back into its initial position.
The postal requirements for digital legibility of a franking imprint must be satisfied with certainty.
It has been empirically established that the strippers previously used in the franking machine of the Centormail® type to clean the wiper lips are often insufficient, such that ink residues dry on the wiper elements. In many cases the dried ink has polluting effects upon a new wiping of the damp heads, which reduce the print quality or possibly could lead to failure of the print head.